The present invention relates to digital watermarking, also called computational watermarking.
Digital watermarking (hereinafter “watermarking”) is a technique wherein information is embedded into a digital file in a way which does not noticeably affect the file contents. Thus a watermark can be inserted into, for example, a media file such as an MPG audio or video file or a JPG still image file without there being any noticeable change in how the audio sounds or what the still image or video looks like.
Watermarks can be applied at the time a file is created—for example, when a CD master is made or when a copy of the file is downloaded to a purchaser from an on-line store—and can used for identification and enforcement purposes. The exact content of the information embedded in the watermark depends on the particular application, but may include the identity of the creator or the distributor of the work, the identity of a person to whom the work was sold, a customer account number, or the licensing terms between seller and purchaser. The information thus embedded can be used to demonstrate content ownership, content misappropriation or as a proof of purchase.
Specifically, a rights holder holds intellectual property rights, such as a copyright, in all or a portion of the contents of many files, such as music files, video files and so forth. The information embedded in the watermark can be “authentication information” that establishes that someone in possession of a copy of the file obtained it in a manner authorized by the rights holder. Such authentication information could have, for example, been inserted into the file at the time of a download by an on-line music store or other distributor who was authorized by the rights holder to distribute copies of the file and might include information about the transaction, as noted above.